I haven't had money this year to buy many TLC figures--I've got a few droid pieces, but none that go together. But then the Target bogo packs come in & so I just finished my first droids: R3-M3 and R5-C7.

I'm sure this has been discussed already, but what's the point of the extra joint hole toward the bottom of the astromech figures?

Targeted more toward the younger collector and meant to "sell" the whole Droid Factory gimmick, the holes are there as an option to add another set of legs or to move the existing pair lower on the body. They allow you to frankenstein your own astromech by mix and matching legs from other astros or arms & legs from protocol droids as well.